By immunizing and boosting rabbits with phenol-inactivated S. aureus and challenging them topically with viable S. aureus, we have established a rabbit modelfor vascularized, elevated nodular infiltrates of the cornea resembling phlyctenules in humans and peripheral corneal infiltrates running parallel to the limbus and separate from it by a lucid interval resembling catarrhal infiltrates in humans. Immunopathological studies of antibody and complement deposition in these lesions will be correlated with their histopathology. We plan to determine the role of an intact corneal epitheIium and to determine if rabbits can be immunized to ?. aureus through the ocular route without systemic immunization with complete Freund's adjuvant since this would most closely resemble the human predicament. We will determine the importance of various strains of staphylococci and the factors they produce and the role of specific staphylococcal antigens such as protein A, ribitol teichoic acid and peptidoglycan in the production of these hypersensitivity lesions of the cornea. Rabbits immunized and challenged with various staphylococcal strains and antigens will be studied for evidence of cell-mediated immunity to protein A, ribitol teichoic acid, peptidoglycan nd sonicated suspensions of various staphylococcal strains by means of thelymphocyte stimulation assay and the leucocyte migration inhibition assay. In addition, titers to these antigens will be determined by double diffusion in agar gel. In this way, the development and progression of corneal lesions can be correlated with antibody levels and cell-mediated immunity to various strains of S. aureus and their antigens. We plan to extend our model to include mice. Athymic mice will be used to assess the importance of T lymphocytes, and mice with absolute deficiencies of either C4 or C5 will be used to determine the importance of complement inthe immunopathogenesis of these lesions.